Rotary compressor with cylinder immersed in oil

ABSTRACT

A rotary compressor ( 100 ) includes a closed casing ( 1 ), a cylinder ( 15 ), a piston ( 28 ), a lower bearing member ( 7 ), a vane ( 33 ), a suction port, a discharge port ( 41 ), and a partition member ( 10 ). The partition member ( 10 ) is attached to a second principal surface ( 7   a ) of the lower bearing member ( 7 ) located on the opposite side to the cylinder ( 15 ) so as to form a refrigerant discharge space ( 52 ) serving as a flow path of a refrigerant discharged from a discharge chamber through the discharge port ( 41 ). The refrigerant discharge space ( 52 ) is limited so that a region where the refrigerant discharge space ( 52 ) is not present is formed on the same side as the suction port with respect to a first reference plane, and in that region, the second principal surface ( 7   a ) of the lower bearing member ( 7 ) is in contact with an oil in an oil reservoir ( 22 ) directly or via the partition member ( 10 ).

TECHNICAL FIELD

The present invention relates to rotary compressors.

BACKGROUND ART

Rotary compressors are widely used in electrical appliances such as airconditioners, heaters, and hot water dispensers. As one approach toimprove the efficiency of rotary compressors, there has been proposed atechnique for suppressing so-called heat loss, i.e., a decrease inefficiency caused by the fact that a refrigerant drawn into acompression chamber (a drawn refrigerant) receives heat from theenvironment.

A rotary compressor of Patent Literature 1 has a closed space providedin a suction-side portion of a cylinder as a means for suppressing heatreception by a drawn refrigerant. The closed space suppresses heattransfer from a high-temperature refrigerant in a closed casing to theinner wall of the cylinder.

CITATION LIST Patent Literature

Patent Literature 1: JP 02(1990)-140486 A

SUMMARY OF INVENTION Technical Problem

However, it is not necessarily easy to form a closed space in a cylinderas in Patent Literature 1. Therefore, another technique capable ofeffectively suppressing heat reception by a drawn refrigerant has beendesired.

Solution to Problem

The present disclosure provides a rotary compressor including:

a closed casing having an oil reservoir;

a cylinder disposed inside the closed casing so as to be immersed in theoil reservoir;

a piston disposed inside the cylinder;

a bearing member disposed above or below the cylinder so as to form acylinder chamber between the cylinder and the piston, the bearing memberhaving a first principal surface that is in contact with the cylinderand a second principal surface that is opposite to the first principalsurface;

a vane that partitions the cylinder chamber into a suction chamber and adischarge chamber;

a suction port though which a refrigerant to be compressed is introducedinto the suction chamber;

a discharge port through which the compressed refrigerant is dischargedfrom the discharge chamber, the discharge port being formed in thebearing member; and

a partition member attached to the second principal surface of thebearing member so as to form, together with the bearing member, arefrigerant discharge space capable of retaining the refrigerantdischarged from the discharge chamber through the discharge port.

In this rotary compressor, when (i) a plane including a central axis ofthe cylinder and a center of the vane when the vane protrudes maximallytoward the central axis of the cylinder is defined as a first referenceplane, (ii) a plane including the central axis and perpendicular to thefirst reference plane is defined as a second reference plane, and (iii)four segments obtained by dividing the rotary compressor by the firstreference plane and the second reference plane are defined as a firstquadrant segment including the suction port, a second quadrant segmentincluding the discharge port, a third quadrant segment opposite to thefirst quadrant segment and adjacent to the second quadrant segment, anda fourth quadrant segment opposite to the second quadrant segment andadjacent to the first quadrant segment, respectively,

the refrigerant discharge space falls within a combined regionconsisting of a region corresponding to the first quadrant segment, aregion corresponding to the second quadrant segment, and a regioncorresponding to the third quadrant segment, and

the second principal surface of the bearing member is in contact with anoil in the oil reservoir directly or via the partition member over anextended region defined by extending a region corresponding to thefourth quadrant segment circumferentially around the central axis to therefrigerant discharge space.

Advantageous Effects of Invention

According to the above rotary compressor, the refrigerant dischargespace is limited so that a region where the refrigerant discharge spaceis not present is formed on the same side as the suction port withrespect to the first reference plane, and in that region, the secondprincipal surface of the bearing member located on the opposite side tothe cylinder is in contact with the oil in the oil reservoir. With sucha configuration, it is possible to reduce the cross-sectional area of aheat transfer path from the discharged refrigerant to the drawnrefrigerant and to increase the distance over which the heat istransferred. Therefore, it is possible to suppress the heat transferfrom the compressed refrigerant to the drawn refrigerant through thebearing member.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a longitudinal cross-sectional view of a rotary compressoraccording to a first embodiment of the present invention.

FIG. 2A is a transverse cross-sectional view of the rotary compressorshown in FIG. 1 taken along the line IIA-IIA.

FIG. 2B is a transverse cross-sectional view of the rotary compressorshown in FIG. 1 taken along the line IIB-IIB.

FIG. 3 is a bottom view of a lower bearing member used in the rotarycompressor shown in FIG. 1.

FIG. 4A is a schematic diagram illustrating another method fordetermining the position of a refrigerant discharge space.

FIG. 4B is a schematic diagram illustrating another method fordetermining the position of the refrigerant discharge space.

FIG. 4C is a schematic diagram illustrating another method fordetermining the position of the refrigerant discharge space.

FIG. 4D is a schematic diagram showing another desired position of therefrigerant discharge space.

FIG. 4E is a schematic diagram showing still another desired position ofthe refrigerant discharge space.

FIG. 5 is a longitudinal cross-sectional view of a rotary compressoraccording to a modification.

FIG. 6 is a bottom view of a lower bearing member used in the rotarycompressor shown in FIG. 5.

FIG. 7 is a longitudinal cross-sectional view of a rotary compressoraccording to a second embodiment of the present invention.

FIG. 8 is a bottom view of a lower bearing member used in the rotarycompressor shown in FIG. 7.

FIG. 9 is a longitudinal cross-sectional view of a rotary compressoraccording to still another embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

A first aspect of the present disclosure provides a rotary compressorincluding:

a closed casing having an oil reservoir;

a cylinder disposed inside the closed casing so as to be immersed in theoil reservoir;

a piston disposed inside the cylinder;

a bearing member disposed above or below the cylinder so as to form acylinder chamber between the cylinder and the piston, the bearing memberhaving a first principal surface that is in contact with the cylinderand a second principal surface that is opposite to the first principalsurface;

a vane that partitions the cylinder chamber into a suction chamber and adischarge chamber;

a suction port through which a refrigerant to be compressed isintroduced into the suction chamber;

a discharge port through which the compressed refrigerant is dischargedfrom the discharge chamber, the discharge port being formed in thebearing member; and

a partition member attached to the second principal surface of thebearing member so as to form, together with the bearing member, arefrigerant discharge space capable of retaining the refrigerantdischarged from the discharge chamber through the discharge port.

In this rotary compressor, when (i) a plane including a central axis ofthe cylinder and a center of the vane when the vane protrudes maximallytoward the central axis of the cylinder is defined as a first referenceplane, (ii) a plane including the central axis and perpendicular to thefirst reference plane is defined as a second reference plane, and (iii)four segments obtained by dividing the rotary compressor by the firstreference plane and the second reference plane are defined as a firstquadrant segment including the suction port, a second quadrant segmentincluding the discharge port, a third quadrant segment opposite to thefirst quadrant segment and adjacent to the second quadrant segment, anda fourth quadrant segment opposite to the second quadrant segment andadjacent to the first quadrant segment, respectively,

the refrigerant discharge space falls within a combined regionconsisting of a region corresponding to the first quadrant segment, aregion corresponding to the second quadrant segment, and a regioncorresponding to the third quadrant segment, and

the second principal surface of the bearing member is in contact with anoil in the oil reservoir directly or via the partition member over anextended region defined by extending a region corresponding to thefourth quadrant segment circumferentially around the central axis to therefrigerant discharge space.

A second aspect of the present disclosure provides the rotary compressoraccording to the first aspect, wherein the second principal surface ofthe bearing member is a plane, and a recess into which the dischargeport opens is formed in the second principal surface, the recess havinga depth larger than a half of a distance between the first principalsurface and the second principal surface. Such a configuration isdesirable from the viewpoint of providing a thermal barrier layer madeof the material (usually a metal) of the bearing member through the useof the thickness of the bearing member.

A third aspect of the present disclosure provides the rotary compressoraccording to the first aspect, wherein a recess into which the dischargeport opens is formed in the second principal surface of the bearingmember, and a cutout is formed in the second principal surface on theopposite side to the recess with respect to the central axis. The cutoutthus formed reduces the thickness of the bearing member, and thusreduces the weight of the bearing member.

A fourth aspect of the present disclosure provides the rotary compressoraccording to the second or third aspect, wherein the partition memberincludes a single plate-like member, and the recess formed in the secondprincipal surface is closed by the partition member so as to form therefrigerant discharge space. This structure is very simple and thereforean increase in the number of components can be avoided.

A fifth aspect of the present disclosure provides the rotary compressoraccording to the first aspect, wherein the bearing member is disposedbelow the cylinder and includes a circular plate portion that definesthe first principal surface and the second principal surface and aprotruding portion that protrudes downward at a center of the circularplate portion, and the partition member has a shape enclosing thedischarge port together with a space facing the second principal surfaceof the bearing member, and the space enclosed by the bearing member andthe partition member constitutes the refrigerant discharge space. Withsuch a structure, it is possible to limit the refrigerant dischargespace and thus to allow the second principal surface of the bearingmember to be in contact with the oil in the oil reservoir directly orvia the partition member, while the bearing member having the samestructure as a bearing member for a conventional rotary compressor isused.

A sixth aspect of the present disclosure provides the rotary compressoraccording to any one of the first to fifth aspects, wherein when (a) aplane including the central axis and a center of the suction port isdefined as a third reference plane, (b) one of two segments obtained bydividing the rotary compressor by the first reference plane is definedas a first high-temperature segment including the discharge port, (c)one of two segments obtained by dividing the rotary compressor by thethird reference plane is defined as a second high-temperature segmentincluding the discharge port, and (d) three of four segments obtained bydividing the rotary compressor by the first reference plane and thethird reference plane are collectively defined as a combinedhigh-temperature segment, the three segments being included in the firsthigh-temperature segment or the second high-temperature segment, in aprojection view obtained by projecting the combined high-temperaturesegment and the refrigerant discharge space onto a plane perpendicularto the central axis, 70% or more of a region corresponding to therefrigerant discharge space overlaps a region corresponding to thecombined high-temperature segment. With such a configuration, the totalloss including heat reception by the drawn refrigerant (heat loss) andpressure loss can be minimized.

A seventh aspect of the present disclosure provides the rotarycompressor according to any one of the first to sixth aspects, whereinthe rotary compressor further includes a shaft to which the piston isfitted. This rotary compressor can be a vertical rotary compressor inwhich a rotational axis of the shaft is parallel to a direction ofgravity and the oil reservoir is formed at a bottom of the closedcasing. In the vertical rotary compressor, the oil in the oil reservoiris less likely to be affected by swirling flow generated by a motor thatdrives the shaft.

Hereinafter, embodiments of the present invention will be described withreference to the drawings. The present invention is not limited to theembodiments given below.

(First Embodiment)

As shown in FIG. 1, a rotary compressor 100 of the present embodimentincludes a closed casing 1, a motor 2, a compression mechanism 102, anda shaft 4. The compression mechanism 102 is disposed in the lower partof the closed casing 1. The motor 2 is disposed above the compressionmechanism 102 inside the closed casing 1. The compression mechanism 102and the motor 2 are coupled together by the shaft 4. A terminal 21 forsupplying electric power to the motor 2 is provided on the upper part ofthe closed casing 1. An oil reservoir 22 for holding lubricating oil isformed at the bottom of the closed casing 1.

The motor 2 is composed of a stator 17 and a rotor 18. The stator 17 isfixed to the inner wall of the closed casing 1. The rotor 18 is fixed tothe shaft 4, and rotates together with the shaft 4.

A discharge pipe 11 is provided in the upper part of the closed casing1. The discharge pipe 11 penetrates the upper part of the closed casing1, and opens into an internal space 13 of the closed casing 1. Thedischarge pipe 11 serves as a discharge flow path for discharging therefrigerant compressed in the compression mechanism 102 to the outsideof the closed casing 1. During the operation of the rotary compressor100, the internal space 13 of the closed casing 1 is filled with thecompressed refrigerant.

The compression mechanism 102 is driven by the motor 2 to compress therefrigerant. Specifically, the compression mechanism 102 has a firstcompression block 3, a second compression block 30, an upper bearingmember 6, a lower bearing member 7, an intermediate plate 38, a firstpartition member 9 (a first muffler or a first closing member), and asecond partition member 10 (a second muffler or a second closingmember). The refrigerant is compressed in the first compression block 3or the second compression block 30. The first compression block 3 andthe second compression block 30 are immersed in the oil stored in theoil reservoir 22. In the present embodiment, the first compression block3 is composed of the same components as those of the second compressionblock 30. Therefore, the first compression block 3 has the same suctionvolume as that of the second compression block 30.

As shown in FIG. 2A, the first compression block 3 is composed of afirst cylinder 5, a first piston 8, a first vane 32, a first suctionport 19, a first discharge port 40, and a first spring 36. As shown inFIG. 2B, the second compression block 30 is composed of a secondcylinder 15, a second piston 28, a second vane 33, a second suction port20, a second discharge port 41, and a second spring 37. The firstcylinder 5 and the second cylinder 15 are disposed vertically andconcentrically.

The shaft 4 has a first eccentric portion 4 a and a second eccentricportion 4 b. The eccentric portions 4 a and 4 b each protrude radiallyoutward. The first piston 8 and the second piston 28 are disposed insidethe first cylinder 5 and the second cylinder 15, respectively. In thefirst cylinder 5, the first piston 8 is fitted to the first eccentricportion 4 a. In the second cylinder 15, the second piston 28 is fittedto the second eccentric portion 4 b. A first vane groove 34 and a secondvane groove 35 are formed in the first cylinder 5 and the secondcylinder 15, respectively. In the rotational direction of the shaft 4,the position of the first vane groove 34 coincides with the position ofthe second vane groove 35. The first eccentric portion 4 a protrudes ina direction 180 degrees opposite to the direction in which the secondeccentric portion 4 b protrudes. That is, the phase difference betweenthe first piston 8 and the second piston 28 is 180 degrees. Thisconfiguration is effective in reducing vibration and noise.

The upper bearing member 6 is disposed above the first cylinder 5 so asto form a first cylinder chamber 25 between the inner circumferentialsurface of the first cylinder 5 and the outer circumferential surface ofthe first piston 8. The lower bearing member 7 is disposed below thesecond cylinder 15 so as to form a second cylinder chamber 26 betweenthe inner circumferential surface of the second cylinder 15 and theouter circumferential surface of the second piston 28. Morespecifically, the upper bearing member 6 is attached to the uppersurface of the first cylinder 5, and the lower bearing member 7 isattached to the lower surface of the second cylinder 15. Theintermediate plate 38 is disposed between the first cylinder 5 and thesecond cylinder 15. The upper bearing member 6 has a first principalsurface 6 b that is in contact with the first cylinder 5 and a secondprincipal surface 6 a that is opposite to the first principal surface 6b and parallel to the first principal surface 6 b. The lower bearingmember 7 has a first principal surface 7 b that is in contact with thesecond cylinder 15 and a second principal surface 7 a that is oppositeto the first principal surface 7 b and parallel to the first principalsurface 7 b.

The first suction port 19 and the second suction port 20 are formed inthe first cylinder 5 and the second cylinder 15, respectively. The firstsuction port 19 and the second suction port 20 open into the firstcylinder chamber 25 and the second cylinder chamber 26, respectively. Afirst suction pipe 14 and a second suction pipe 16 are connected to thefirst suction port 19 and the second suction port 20, respectively.

The first discharge port 40 and the second discharge port 41 are formedin the upper bearing member 6 and the lower bearing member 7,respectively. The first discharge port 40 and the second discharge port41 open into the first cylinder chamber 25 and the second cylinderchamber 26, respectively. The first discharge port 40 is provided with afirst discharge valve 43 so as to open and close the first dischargeport 40. The second discharge port 41 is provided with a seconddischarge valve 44 so as to open and close the second discharge port 41.

A first vane 32 (blade) is slidably fitted in the first vane groove 34.The first vane 32 partitions the first cylinder chamber 25 in thecircumferential direction of the first piston 8. That is, the firstcylinder chamber 25 is partitioned into a first suction chamber 25 a anda first discharge chamber 25 b. A second vane 33 (blade) is slidablyfitted in the second vane groove 35. The second vane 33 partitions thesecond cylinder chamber 26 in the circumferential direction of thesecond piston 28. That is, the second cylinder chamber 26 is partitionedinto a second suction chamber 26 a and a second discharge chamber 26 b.The first suction port 19 is located on one side of the first vane 32and the first discharge port 40 is located on the other side thereof.The second suction port 20 is located on one side of the second vane 33and the second discharge port 41 is located on the other side thereof.The refrigerant to be compressed is supplied to the first cylinderchamber 25 (first suction chamber 25 a) through the first suction port19. The refrigerant to be compressed is supplied to the second cylinderchamber 26 (second suction chamber 26 a) through the second suction port20. The refrigerant compressed in the first cylinder chamber 25 pushesthe first discharge valve 43 open, and is discharged from the firstdischarge chamber 25 b through the first discharge port 40. Therefrigerant compressed in the second cylinder chamber 26 pushes thesecond discharge valve 44 open, and is discharged from the seconddischarge chamber 26 b through the second discharge port 41.

The first piston 8 and the first vane 32 may constitute a singlecomponent, a so-called swing piston. The second piston 28 and the secondvane 33 may constitute a single component, a so-called swing piston. Thefirst vane 32 and the second vane 33 may be coupled to the first piston8 and the second piston 28, respectively. The specific type of therotary compressor is not particularly limited, and a wide variety oftypes of rotary compressors, such as a rolling piston type rotarycompressor and a swing piston type rotary compressor, can be used.

The first spring 36 and the second spring 37 are disposed behind thefirst vane 32 and the second vane 33, respectively. The first spring 36and the second spring 37 push the first vane 32 and the second vane 33,respectively, toward the center of the shaft 4. The rear end of thefirst vane groove 34 and the rear end of the second vane groove 35 eachcommunicate with the internal space 13 of the closed casing 1.Therefore, the pressure in the internal space 13 of the closed casing 1is applied to the rear surface of the first vane 32 and the rear surfaceof the second vane 33. The oil stored in the oil reservoir 22 issupplied to the first vane groove 34 and the second vane groove 35.

As shown in FIG. 1, the first partition member 9 is attached to thesecond principal surface 6 a of the upper bearing member 6 so as toform, on the opposite side to the first cylinder chamber 25 with respectto the upper bearing member 6, a refrigerant discharge space 51 capableof retaining the refrigerant discharged from the first discharge chamber25 b through the first discharge port 40. The first partition member 9,together with the upper bearing member 6, forms the refrigerantdischarge space 51. The first discharge valve 43 is covered by the firstpartition member 9. An opening 9 a, for introducing the refrigerant fromthe refrigerant discharge space 51 into the internal space 13 of theclosed casing 1, is formed in the first partition member 9. The secondpartition member 10 is attached to the second principal surface 7 a ofthe lower bearing member 7 so as to form, on the opposite side to thesecond cylinder chamber 26 with respect to the lower bearing member 7, arefrigerant discharge space 52 capable of retaining the refrigerantdischarged from the second discharge chamber 26 b through the seconddischarge port 41. The second partition member 10, together with thelower bearing member 7, forms the refrigerant discharge space 52. Thesecond discharge valve 44 is covered by the second partition member 10.The refrigerant discharge spaces 51 and 52 each serve as a flow path forthe refrigerant. The shaft 4 penetrates the central portion of the firstpartition member 9 and the central portion of the second partitionmember 10, and is rotatably supported by the upper bearing member 6 andthe lower bearing member 7. It should be noted that in the upper bearingmember 6, a bearing portion that rotatably supports the shaft 4protrudes upward at the center of the second principal surface 6 a.

The refrigerant discharge space 52 communicates with the refrigerantdischarge space 51 via a through flow path 46 (not shown in FIG. 1). Thethrough flow path 46 penetrates through the lower bearing member 7, thesecond cylinder 15, the intermediate plate 38, the first cylinder 5, andthe upper bearing member 6, in a direction parallel to the rotationalaxis of the shaft 4. The refrigerant compressed in the secondcompression block 30 and the refrigerant compressed in the firstcompression block 3 are merged together in the internal space of thefirst partition member 9, that is, the refrigerant discharge space 51.Therefore, even if the volume of the refrigerant discharge space 52 isslightly smaller than the required volume, the silencing effect by therefrigerant discharge space 51 can be obtained within the firstpartition member 9. The cross-sectional area of the through flow path 46(flow path area) is larger than the cross-sectional area (flow patharea) of the second discharge port 41. Therefore, an increase in thepressure loss can be prevented.

As shown in FIG. 2B, in the present description, a first reference planeH₁, a second reference plane H₂, and a third reference plane H₃ aredefined as follows. A plane including the central axis O₁ of the secondcylinder 15 and the center of the second vane 33 when the second vane 33protrudes maximally toward the central axis O₁ of the second cylinder 15is defined as the first reference plane H₁. The first reference plane H₁passes through the center of the second vane groove 35. A planeincluding the central axis O₁ and perpendicular to the first referenceplane H₁ is defined as the second reference plane H₂. A plane includingthe central axis O₁ and the center of the second suction port 20 isdefined as the third reference plane H₃. The central axis O₁ of thesecond cylinder 15 almost coincides with the rotational axis of theshaft 4 and the central axis of the first cylinder 5.

The second vane groove 35 has an opening that faces the second cylinderchamber 26. When the position of the center of the opening of the secondvane groove 35 is defined as a reference position in the circumferentialdirection of the inner circumferential surface of the second cylinder15, the first reference plane H₁ can be a plane passing through thisreference position and including the central axis O₁. That is, the“center of the second vane groove 35” refers to the center of theopening of the second vane groove 35. The first reference plane H₁ canbe a plane including the central axis O₁ of the second cylinder 15 and apoint of contact (specifically, a tangent line) between the secondcylinder 15 and the second piston 28 when the second vane 33 protrudesmaximally toward the central axis O₁ of the second cylinder 15. Thecentral axis O₁ of the second cylinder 15 specifically refers to thecentral axis of the cylindrical inner circumferential surface of thesecond cylinder 15.

In the rotary compressor 100, the level of the oil in the oil reservoir22 is higher than the lower surface of the first cylinder 5. In order toensure reliability, it is desirable that the level of the oil in the oilreservoir 22 be higher than the upper surface of the first cylinder 5and lower than the lower end of the motor 2 during the operation. Thesecond cylinder 15, the lower bearing member 7, and the second partitionmember 10 are immersed in the oil in the oil reservoir 22.

The refrigerant to be compressed is in a low-temperature andlow-pressure state. On the other hand, the compressed refrigerant is ina high-temperature and high-pressure state. Therefore, during theoperation of the rotary compressor 100, the lower bearing member 7 has acertain temperature distribution. Specifically, when the lower bearingmember 7 is divided into a suction-side portion and a discharge-sideportion, the former has a relatively low temperature and the latter hasa relatively high temperature. When the lower bearing member 7 isdivided into two parts by the first reference plane H₁, the suction-sideportion is one part including a portion directly below the secondsuction port 20. The discharge-side portion is the other part having thesecond discharge port 41 formed therein.

In the present embodiment, the refrigerant discharge space 52 is limitedso that a region where the refrigerant discharge space 52 is not presentis formed on the same side as the second suction port 20 with respect tothe first reference plane H₁, and in that region, the second principalsurface 7 a of the lower bearing member 7 is in contact with the oil inthe oil reservoir 22 via the second partition member 10. Since the oilin the oil reservoir 22 is more viscous and less fluid than therefrigerant, the heat transfer coefficient on the second principalsurface 7 a is relatively low. Therefore, the amount of heat transferredfrom the oil to the drawn refrigerant is relatively small. In addition,it is possible to reduce the cross-sectional area of the heat transferpath through which the heat of the discharged refrigerant is transferredto the drawn refrigerant by replacing the space where the dischargedrefrigerant should be present in a conventional rotary compressor by ametallic material (i.e., the lower bearing member 7). In other words, inthe present embodiment, the area of contact between the dischargedrefrigerant and the lower bearing member 7 is small. It is furtherpossible to increase the distance over which the heat of the dischargedrefrigerant is transferred to the drawn refrigerant. More specifically,the heat needs to be transferred through a heat transfer path inside thelower bearing member 7 to transfer the heat from the dischargedrefrigerant in the refrigerant discharge space 52 to the drawnrefrigerant in the second suction chamber 26 a. In the presentembodiment, the heat transfer path is relatively long. According to theFourier's law, the amount of heat transfer is proportional to thecross-sectional area of the heat transfer path and inverselyproportional to the distance of the heat transfer path. This means thatthe present embodiment makes it possible to increase the heat resistanceof the heat transfer from the discharged refrigerant to the drawnrefrigerant. Therefore, it is possible to suppress the heat transferfrom the compressed refrigerant to the drawn refrigerant through thelower bearing member 7. The refrigerant discharge space 52 is describedbelow in further detail.

As shown in FIG. 2B, when the rotary compressor 100 is divided into foursegments by the first reference plane H₁ and the second reference planeH₂, and one of the four segments that includes the second suction port20 is defined as a first quadrant segment Q₁. One of the four segmentsthat includes the second discharge port 41 is defined as a secondquadrant segment Q₂. One of the four segments that is opposite to thefirst quadrant segment Q₁ and adjacent to the second quadrant segment Q₂is defined as a third quadrant segment Q₃. One of the four segments thatis opposite to the second quadrant segment Q₂ and adjacent to the firstquadrant segment Q₁ is defined as a fourth quadrant segment Q₄.

FIG. 3 is a bottom view of the lower bearing member 7. FIG. 4corresponds to the projection view obtained by (orthogonally) projectingthe first to fourth quadrant segments Q₁ to Q₄ and the refrigerantdischarge space 52 onto a plane perpendicular to the central axis O₁,although right and left are reversed in FIG. 3 and the projection view.

In the present embodiment, the entire refrigerant discharge space 52falls within a combined region consisting of a region corresponding tothe first quadrant segment Q₁, a region corresponding to the secondquadrant segment Q₂, and a region corresponding to the third quadrantsegment Q₃. The second principal surface 7 a of the lower bearing member7 is in contact with the oil in the oil reservoir 22 via the secondpartition member 10 over the entire extended region Q₅ defined byextending a region corresponding to the fourth quadrant segment Q₄circumferentially around the central axis O₁ to the refrigerantdischarge space 52.

In the present embodiment, the second principal surface 7 a of the lowerbearing member 7 is a plane of the same size as the first principalsurface 7 b, and the lower bearing member 7 is in the form of a platewith a constant thickness. A recess 7 s extending from the seconddischarge port 41 in both circumferential directions along the innercircumferential surface 15 h of the second cylinder 15 is formed in thesecond principal surface 7 a of the lower bearing member 7. This recess7 s is closed by the second partition member 10 and thereby therefrigerant discharge space 52 is formed. That is, the second dischargeport 41 opens into the recess 7 s. From the viewpoint of providing athermal barrier layer made of the material (usually a metal) of thelower bearing member 7 through the use of the thickness of the lowerbearing member 7, it is desirable that the lower bearing member 7 has arelatively large thickness and the recess 7 s has a depth larger than ahalf of the distance between the first principal surface 7 b and thesecond principal surface 7 a. The second partition member 10 includes asingle plate-like member, and is in close contact with and covers thesecond principal surface 7 a of the lower bearing member 7. Thisstructure is very simple and therefore the lower bearing member 7 andthe second partition member 10 can be produced inexpensively.

It is desirable that most of the refrigerant discharge space 52 beformed on the same side as the second discharge port 41 with respect tothe first reference plane H₁. As described above, the regionscorresponding to the second quadrant segment Q₂ and the third quadrantsegment Q₃ correspond to the discharge-side portion having a relativelyhigh temperature. It makes a certain amount of sense that therefrigerant discharge space 52 is formed in the second quadrant segmentQ₂ and the third quadrant segment Q₃. The through flow path 46 opensinto the refrigerant discharge space 52 in the third quadrant segmentQ₃, for example. The through flow path 46 may open into the refrigerantdischarge space 52 in the second quadrant segment Q₂.

In the present embodiment, the refrigerant discharge space 52 extendsbeyond the first reference plane H₁ and overlaps the third referenceplane H₃. This means that a part of the refrigerant discharge space 52is located directly below the second suction port 20. Such aconfiguration is not necessarily desirable in suppressing heat transfer(heat loss) from the refrigerant in the refrigerant discharge space 52to the refrigerant in the second cylinder chamber 26. However, thisconfiguration can be accepted for the following reason.

In a typical rotary compressor, a suction port and a discharge port areprovided as close to a vane as possible in order to avoid formation of adead volume. The refrigerant discharge space is formed below the lowerbearing member, and the discharge port opens into the refrigerantdischarge space. It is desirable that the refrigerant discharge space beformed only on the same side as the discharge port with respect to thefirst reference plane H₁ in order to reduce the heat loss. On the otherhand, in order to reduce the pressure loss, it is desirable that therebe a sufficiently large space around the discharge port. If the range ofthe refrigerant discharge space is limited in view of the heat loss, thespace around the discharge port becomes insufficient, which may cause asignificant increase in the pressure loss. That is, there is a trade-offrelationship between the reduction of the heat loss and the reduction ofthe pressure loss.

In the present embodiment, a part of the refrigerant discharge space 52is allowed to be located directly below the second suction port 20 forthe purpose of reducing the pressure loss. The effect of reducing theheat loss can be obtained at least as long as the refrigerant dischargespace 52 is not present in the region corresponding to the fourthquadrant segment Q₄.

From another point of view, the position of the refrigerant dischargespace 52 can be determined in the following manner.

As shown in FIG. 4A, the rotary compressor 100 is divided into twosegments by the first reference plane H₁, and one of the two segmentsthat includes the second discharge port 41 is defined as a firsthigh-temperature segment SG₁ (shaded portion). As shown in FIG. 4B, therotary compressor 100 is divided into two segments by the thirdreference plane H₃, and one of the two segments that includes the seconddischarge port 41 is defined as a second high-temperature segment SG₂(shaded portion). As shown in FIG. 4C, the rotary compressor 100 isdivided into four segments by the first reference plane H₁ and the thirdreference plane H₃, and three of the four segments that are included inthe first high-temperature segment SG₁ or the second high-temperaturesegment SG₂ are collectively defined as a combined high-temperaturesegment SG_(total) (shaded portion).

In a projection view obtained by projecting the combinedhigh-temperature segment SG_(total) and the refrigerant discharge space52 onto a plane perpendicular to the central axis O₁, for example, 70%or more of the region corresponding to the refrigerant discharge space52 may overlap the region corresponding to the combined high-temperaturesegment SG_(total). That is, when a part of the refrigerant dischargespace 52 is located directly below the second suction port 20, the totalloss including the heat loss and the pressure loss is minimized, whichmay allow the rotary compressor 100 to exhibit the highest efficiency.

As shown in FIG. 4D, in a projection view obtained by projecting thecombined high-temperature segment SG_(total) and the refrigerantdischarge space 52 onto a plane perpendicular to the central axis O₁,the entire region corresponding to the refrigerant discharge space 52may fall within the region corresponding to the combinedhigh-temperature segment SG_(total). To put it more simply, therefrigerant discharge space 52 may be formed on the opposite side to thesecond cylinder chamber 26 with respect to the lower bearing member 7(below the lower bearing member 7) without extending beyond the thirdreference plane H₃. With such a structure, the effect of suppressing theheat loss is enhanced. If there is no concern about an increase in thepressure loss, such a structure is reasonably acceptable.

In some cases, as shown in FIG. 4E, in a projection view obtained byprojecting the first high-temperature segment SG₁ and the refrigerantdischarge space 52 onto a plane perpendicular to the central axis O₁,the entire region corresponding to the refrigerant discharge space 52may fall within the region corresponding to the first high-temperaturesegment SG₁. This means that the refrigerant discharge space 52 may beformed only on the same side as the second discharge port 41 withrespect to the first reference plane H₁.

The rotary compressor 100 of the present embodiment is a vertical rotarycompressor. During the operation of the rotary compressor 100, therotational axis of the shaft 4 is parallel to the direction of gravity,and the oil reservoir 22 is formed at the bottom of the closed casing 1.During the operation of the rotary compressor 100, the upper portion ofthe oil in the oil reservoir 22 has a relatively high temperature andthe lower portion of the oil in the oil reservoir 22 has a relativelylow temperature. Therefore, according to the vertical rotary compressor100, it is possible to obtain the full advantages of the presentembodiment.

(Modifications)

In the embodiment described above, the second principal surface 7 a ofthe lower bearing member 7 is in contact with the oil in the oilreservoir 22 via the second partition member 10 over the entire extendedregion Q₅. However, the second principal surface 7 a of the lowerbearing member 7 may be in direct contact with the oil in the oilreservoir 22 in the entire extended region Q₅ or a part thereof. Forexample, as in a rotary compressor 200 of a modification shown in FIG. 5and FIG. 6, a fan-shaped cutout 71 may be provided in the secondprincipal surface 7 a of the lower bearing member 7 on the opposite sideto the refrigerant discharge space 52 with respect to the central axisO₁ so that the cutout 71 and the refrigerant discharge space 52 arespaced from each other with a partition wall interposed therebetween,and thereby the second partition member 10 may cover a part of thesecond principal surface 7 a of the lower bearing member 7 other thanthe part corresponding to the cutout 71. Alternatively, even in the casewhere the cutout 71 is provided in the second principal surface 7 a ofthe lower bearing member 7, the second partition member 10 may be formedin a recessed shape conforming to the shape of the cutout 71, andthereby the second partition member 10 may cover the entire secondprincipal surface 7 a of the lower bearing member 7. The cutout 71 thusformed reduces the thickness of the lower bearing member 7. In thiscase, the weight of the lower bearing member 7 is reduced.

(Second Embodiment)

Next, a rotary compressor 300 according to the second embodiment of thepresent invention is described with reference to FIG. 7 and FIG. 8. Inthe present embodiment, the same components as those in the firstembodiment are denoted by the same reference numerals, and thedescription thereof is omitted.

In the present embodiment, the rotary compressor 300 includes a lowerbearing member 70 and a second partition member 60. The rotarycompressor 300 and the rotary compressor 100 shown in FIG. 1 have thesame fundamental structure required to compress a refrigerant.

The lower bearing member 70 is disposed below the second cylinder 15 soas to form the second cylinder chamber 26 between the innercircumferential surface of the second cylinder 15 and the outercircumferential surface of the second piston 28. More specifically, thelower bearing member 70 is attached to the lower surface of the secondcylinder 15. The lower bearing member 70 is composed of a circular plateportion 72 and a bearing portion (protruding portion) 73. The circularplate portion 72 is a thin flat portion adjacent to the second cylinder15, and defines a first principal surface 70 b of the lower bearingmember 70 that is in contact with the second cylinder 15 and a secondprincipal surface 70 b of the lower bearing member 70 that is oppositeto the first principal surface 70 b and parallel to the first principalsurface 70 b. The bearing portion 73 protrudes downward at the center ofthe circular plate portion 72. The second discharge port 41 is formed inthe circular plate portion 72. The second discharge valve 44 that opensand closes the second discharge port 41 is attached to the circularplate portion 72. In the present embodiment, a stepped portion 74forming a recess in a region including the discharge port 41 and thethrough flow path 46 is provided on the second principal surface 70 adefined by the circular plate portion 72. The bearing portion 73 is acylindrical portion that is formed integrally with the circular plateportion 72 so as to support the shaft 4.

The second partition member 60 is a member of a bowl-shaped structure,and is attached to the second principal surface 70 a of the lowerbearing member 70 so as to form the refrigerant discharge space 52 onthe opposite side to the second cylinder chamber 26. More specifically,the second partition member 60 has a shape enclosing the seconddischarge port 41 together with a space facing the second principalsurface 70 a of the lower bearing member 70, and the space enclosed bythe lower bearing member 70 and the second partition member 60constitutes the refrigerant discharge space 52. The second partitionmember 60 also covers the bearing portion 73, and a through hole forexposing the lower end of the shaft 4 to the oil reservoir 22 is formedat the center of the second partition member 60.

Also in the present embodiment, as in the first embodiment, the entirerefrigerant discharge space 52 falls within the combined regionconsisting of the region corresponding to the first quadrant segment Q₁,the region corresponding to the second quadrant segment Q₂, and theregion corresponding to the third quadrant segment Q₃. The secondprincipal surface 70 a of the lower bearing member 70 is in contact withthe oil in the oil reservoir 22 via the second partition member 10 overthe entire extended region Q₅ defined by extending the regioncorresponding to the fourth quadrant segment Q₄ circumferentially aroundthe central axis O₁ to the refrigerant discharge space 52.

The second partition member 60 is composed of a bowl-shaped portion 61and a flange portion 62. The bowl-shaped portion 61 and the flangeportion 62 constitute a single component. The bowl-shaped portion 61 hasa fan shape larger than that of the stepped portion 74 in plane view,and is composed of a bottom wall and a peripheral wall. The bottom wallcovers a specific portion including the stepped portion 74 (for example,about a half) in the second principal surface 70 a with a space betweenthe specific portion and the bottom wall. The peripheral wall extendsupwardly from the periphery of the bottom wall. In the presentembodiment, the bearing portion 73 of the lower bearing member 70 iscontained in the bowl-shaped portion 61, the bottom wall of thebowl-shaped portion 61 is in close contact with the lower surface of thebearing portion 73, and the peripheral wall of the bowl-shaped portion61 is in close contact with about a half of the outer circumferentialsurface of the bearing portion 73. The flange portion 62 is in closecontact with and covers the remaining part of the second principalsurface 7 a.

According to the configuration of the present embodiment, it is possibleto limit the refrigerant discharge space 52 and to allow the secondprincipal surface 70 a of the lower bearing member 70 to be in contactwith the oil in the oil reservoir 22 via the second partition member 60in at least the entire region corresponding to the fourth quadrantsegment Q₄, while the lower bearing member 70 having the same structureas the lower bearing member of a conventional rotary compressor is used.In addition, heat transfer from the oil in the oil reservoir 22 to therefrigerant in the second cylinder chamber 26 can be suppressed moreeffectively by the flange portion 62.

(Other Embodiments)

The rotary compressor of the present invention need not necessarily be atwo-stage rotary compressor. The present invention can also be appliedto single-stage rotary compressors such as a rotary compressor obtainedby removing the first compression block 3 from each of the rotarycompressors 100, 200, and 300 shown in FIGS. 1, 5, and 7.

Alternatively, the bearing member of the present invention may be theupper bearing member 6 disposed above the cylinder 15, as in a rotarycompressor 400 shown in FIG. 9. A partition member 90 is attached to thesecond principal surface 6 a of the upper bearing member 6 so as toform, above the upper bearing member 6, the refrigerant discharge space51 capable of retaining the refrigerant discharged from the dischargechamber 25 b through the discharge port 41. An opening 90 a, forintroducing the refrigerant from the refrigerant discharge space 51 intothe internal space 13 of the closed casing 1, is formed in the partitionmember 90. No discharge port is formed in the lower bearing member 75.

A recess into which the discharge port 41 opens is formed in the secondprincipal surface 6 a of the upper bearing member 6. This recessconstitutes the lower half of the refrigerant discharge space 51. Thepartition member 90 bulges upwardly beyond the oil level in the oilreservoir 22 at a position corresponding to the recess so as toconstitute the upper half of the refrigerant discharge space 51, but theother part of the partition member 90 is in close contact with the upperbearing member 6. The refrigerant discharge space 51 falls within thecombined region consisting of the region corresponding to the firstquadrant segment Q₁, the region corresponding to the second quadrantsegment Q₂, and the region corresponding to the third quadrant segmentQ₃. The second principal surface 6 a of the upper bearing member 6 is incontact with the oil in the oil reservoir 22 directly or via thepartition member 90 over the entire extended region Q₅ defined byextending the region corresponding to the fourth quadrant segment Q₄circumferentially around the central axis O₁ to the refrigerantdischarge space 51.

The advantageous effects of the present invention can also be obtainedin the configuration as shown in FIG. 9. It should be noted that if thebearing member of the present invention is a lower partition memberdisposed below the cylinder, as shown in the first and secondembodiments, thermal stratification in the oil reservoir 22 in which thetemperature of the oil decreases in the lower layers can be reasonablyused, and therefore the advantageous effects of the present inventioncan be obtained more significantly.

INDUSTRIAL APPLICABILITY

The present invention is useful for compressors of refrigeration cycleapparatuses that can be used in electrical appliances such as hot waterdispensers, hot water heaters, and air conditioners.

The invention claimed is:
 1. A rotary compressor comprising: a closedcasing comprising an oil reservoir; a cylinder disposed inside theclosed casing so as to be immersed in the oil reservoir; a pistondisposed inside the cylinder; a bearing member disposed below thecylinder so as to form a cylinder chamber between the cylinder and thepiston, the bearing member having a first principal surface that is incontact with the cylinder and a second principal surface that isopposite to the first principal surface; a vane that partitions thecylinder chamber into a suction chamber and a discharge chamber; asuction port through which a refrigerant to be compressed is introducedinto the suction chamber; a discharge port through which the compressedrefrigerant is discharged from the discharge chamber, the discharge portbeing formed in the bearing member; and a partition member attached tothe second principal surface of the bearing member so as to form,together with the bearing member, a refrigerant discharge space thatretains the refrigerant discharged from the discharge chamber throughthe discharge port, wherein when (i) a plane including a central axis ofthe cylinder and a center of the vane when the vane protrudes maximallytoward the central axis of the cylinder is defined as a first referenceplane, (ii) a plane including the central axis and perpendicular to thefirst reference plane is defined as a second reference plane, and (iii)four segments obtained by dividing the rotary compressor by the firstreference plane and the second reference plane are defined as a firstquadrant segment including the suction port, a second quadrant segmentincluding the discharge port, a third quadrant segment opposite to thefirst quadrant segment and adjacent to the second quadrant segment, anda fourth quadrant segment opposite to the second quadrant segment andadjacent to the first quadrant segment, respectively, the refrigerantdischarge space falls within a combined region consisting of a regioncorresponding to the first quadrant segment, a region corresponding tothe second quadrant segment, and a region corresponding to the thirdquadrant segment, the second principal surface of the bearing member isin contact with an oil in the oil reservoir directly or via thepartition member over an extended region defined by extending a regionof the bearing member corresponding to the fourth quadrant segmentcircumferentially around the central axis to the refrigerant dischargespace, a recess extending from the discharge port in bothcircumferential directions along an inner circumferential surface of thecylinder is formed in the second principal surface of the bearingmember, the discharge port opens into the recess, the recess is closedby the partition member and thereby the refrigerant discharge space isformed, a thermal barrier layer including a metal of the bearing memberis formed in the extended region of the bearing member, and the thermalbarrier layer has a constant thickness.
 2. The rotary compressoraccording to claim 1, wherein the recess has a depth larger than a halfof a distance between the first principal surface and the secondprincipal surface.
 3. The rotary compressor according to claim 2,wherein the partition member comprises a single plate-like member. 4.The rotary compressor according to claim 1, wherein the bearing memberis disposed below the cylinder and includes a circular plate portionthat defines the first principal surface and the second principalsurface and a protruding portion that protrudes downward at a center ofthe circular plate portion, and the partition member has a shapeenclosing the discharge port together with a space facing the secondprincipal surface of the bearing member, and the space enclosed by thebearing member and the partition member constitutes the refrigerantdischarge space.
 5. The rotary compressor according to claim 1, whereinwhen (a) a plane including the central axis and a center of the suctionport is defined as a third reference plane, (b) one of two segmentsobtained by dividing the rotary compressor by the first reference planeis defined as a first high-temperature segment including the dischargeport, (c) one of two segments obtained by dividing the rotary compressorby the third reference plane is defined as a second high-temperaturesegment including the discharge port, and (d) three of four segmentsobtained by dividing the rotary compressor by the first reference planeand the third reference plane are collectively defined as a combinedhigh-temperature segment, the three segments are included in the firsthigh-temperature segment or the second high-temperature segment, and ina projection view obtained by projecting the combined high-temperaturesegment and the refrigerant discharge space onto a plane perpendicularto the central axis, 70% or more of a region corresponding to therefrigerant discharge space overlaps a region corresponding to thecombined high-temperature segment.
 6. The rotary compressor according toclaim 1, further comprising a shaft to which the piston is fitted,wherein the rotary compressor is a vertical rotary compressor in which arotational axis of the shaft is parallel to a direction of gravity andthe oil reservoir is formed at a bottom of the closed casing.
 7. Therotary compressor according to claim 1, wherein the refrigerantdischarge space is also located directly below the suction port.